Tony Blair is set to become the first serving prime minister to be interrogated in a criminal inquiry. Robert Winnett reports on the mounting evidence in the cash for peerages affair

Earlier this year the prime minister walked through the glass atrium of Portcullis House, the modern wing of parliament, to face a deeply unwelcome grilling from his own party executive.

In a committee room were waiting 31 members of Labour’s national executive committee (NEC), including MPs, trade unionists and activists. They were shocked and angry after learning from reports in this newspaper how Blair had funded the party’s 2005 election campaign with secret loans from businessmen, some of whom had later been proposed for peerages.

They wanted explanations. Why had Blair agreed to the loans, which ran into millions? Why had he told party chiefs nothing about them? Why did some donors claim the party, not the lenders, had proposed the arrangements? Until now, what Blair told the NEC has never emerged. But this weekend a record of the meeting on